Portable FT-IR spectroscopy Contact sponge method

By overlapping the same area acquired at different time, e.g. before and after a cleaning treatment, it is possible to compare the changes in pattern surfaces Figure 6. The 3D profile of the quotes of the surface is extracted through the DEM of each models. The analysis of the frequency distribution of the quotes on the investigated area allows the extraction of some dimensional information on the surface pattern such as roughness or quote of particular areas maximum and minimum values of elevation. Choosing, by a polyline, a direction on the surface, it’s possible to generate roughness profiles, whose coordinates can be exported in text format and elaborated with any software that allow their graphics processing. 2.1.5 Evanescent Field Dielectrometry The Evanescent Field Dielectrometry EFD is a diagnostic methods based on electromagnetic measurement of the permittivity of the material under investigation. This method has been usefully employed for determining by non-invasive way the moisture and salts content inside materials Olmi R., et al., 2006. The theoretical concept is based on the measurement of the dielectric contrast between water about 80 and the host material in the microwave frequency range. The dielectric constant of typical materials used in masonry brick, plaster, mortar and stone is about 3-5. Thanks to the high dielectric contrast, it is possible to perform a powerful diagnostic of both the moisture content and the soluble salts inside the material up to 2 cm in depth. The measure is carried out in real time, needing some seconds to be completed. The dielectric constant real part of dielectric permittivity determines the ability of the material to polarize itself, or to form and to orient electric dipoles when an external electric field is applied. This behaviour is quantified by the real part of permittivity; on the contrary the imaginary part is related to the dissipative effects due to friction acting between the electric dipoles while chasing the variations of the electric field. The imaginary part also depends on the electrical conductivity of the material, or rather from ions mobility. Therefore, a dry material containing salts can be characterized by a low electrical conductivity, even if the salts are present in high quantity. The proposed system SUSI © tool, USA Patent, Bini et al., 2009 measures independently both the real part and the imaginary part of permittivity in the microwave frequency range. The support is investigated by the electric field that spills out from the aperture of the opened resonant cavity. In this case, the sensor is a truncated coaxial line closed on one side on the resonant circuit and on the other side opened on the material under investigation. Errore. Lorigine riferimento non è stata trovata. shows the setup of the measurement system. It consists of a microwave signal meter on the left in the picture, the probe on the bottom in the picture, and a notebook on which is installed the software to control the instrument, as well as for the real time elaboration. Figure 7. SUSI © tool The measurement is performed keeping in contact the probe with the surface of the material under investigation avoiding areas with risk of detachment or with others criticality. The measurement is averaged on a hemisphere 2 cm depth of radius into the material. Maps in terms of moisture content MC and salinity index SI can be elaborated from the data collected during the survey of the surface under investigation. Figure 8. Maps of MC and SI on the wall paintings “The legend of St. Alex ”, S. Clement church, Rome

2.2 Others techniques

2.2.1 Portable FT-IR spectroscopy

The FTIR analyses can be performed on site by the use of the ALPHA- R spectrometer Bruker Optik footprint 22 cm × 33 cm, weight about 7 kg. The interferometer inside the ALPHA- R spectrometer RockSolidTM has a cubic corner mirrors; therefore, the sensitivity to vibrations is much lower compared with that of standard plane optics used in conventional Michelson ’s interferometers. To collect infrared spectra without touching the surface of the sample, a reflectance head with specular optics and long working distance about 2 cm can be used. The integrated high-resolution camera allowed us to observe the measured spot and to record an image of it. The detector works at room temperature. The spot investigated was circular with a diameter of about 6 mm. The spectral range covered by the instrument is 350 –7,500 cm -1 , with 4 cm -1 spectral resolution. The device has been usefully used to verify the presence and type of protective and consolidant treatments on one experimental wall placed into the archaeological area of Pompeii Figure 9. This contribution has been peer-reviewed. doi:10.5194isprs-archives-XLII-2-W5-665-2017 | © Authors 2017. CC BY 4.0 License. 668 a b Figure 9. a Portable FTIR applied on the wall of the Macellum in the archaeological site of Pompeii; b Reflectance spectra on Campanian Ignimbrite before and after the treatment.

2.2.2 Contact sponge method

The contact sponge method is a water absorption test useful in evaluating differences induced by water repellents treatments Vandevoorde et al., 2009; Tiano Pardini, 2004. The method consists in applying a soaked sponge with a controlled pressure on the surface to be tested. The water needed to soak the sponge is measured in advance; the soaked sponge is weighed, applied and kept in contact for 1-2 minutes depends on the material porosity; then it is weighed again. The weight difference is a measure of the water absorbed by capillarity. The measures are carried out before T and after T 1 the application of the water repellent treatments. This very friendly portable system has been used for monitoring the behaviour of two different protectives applied on testing areas of the Ratto delle Sabine, a marble statue of Giambologna placed in the Loggia dei Lanzi Piazza Signoria, Firenze, Italy, Figure 11. After the application of two repellent products the water absorption is decreased, even if not at the same level for each protective; monitoring the efficiency and the durability of the treatments we can see Figure 11 that, after about 60 months, while product S retains almost its water repellency the product W has loosed it for about 30. Figure 10. Contact sponge applied on a testing areas for the evaluation of water repellency of the protective treatments applied on the Marble statue of Ratto delle Sabine, Loggia dei Lanzi, Firenze, Italy Figure 11. Water repellency monitoring, by the Contact Sponge, of the two protective treatments applied on the marble statue of Ratto delle Sabine

2.2.3 Drilling Resistance Measurements System